Case study: Upgrading a hospital’s EPSS

A 250-bed trauma center hospital campus needed an upgrade to the emergency power supply system equipment to replace aging infrastructure and improve system reliability. The existing EPSS equipment consisted of more than 20 automatic transfer switches and associated distribution panels and transformers connected to paralleled diesel generator sets located in a remote central utility plant.

The equipment was divided into two locations. The electrical rooms in both locations contained both EPSS and normal service equipment in the form of 15-kilovolt switchgear, unit substations and normal service switchboards. This was commonplace at the time of construction but the 2019 edition of NFPA 110: Standard for Emergency and Standby Power Systems section 7.2.3 requires that the EPSS equipment be located in a separate room from normal service equipment (when the voltage is greater than 150 volts to ground and the amperage is greater than 1,000 amperes. These rooms had both conditions.

The intent of this section of code is to prevent a catastrophic failure of the normal service equipment from damaging the EPSS equipment. When evaluating this condition, engineers should factor in the nature of the occupancy and the risk to building occupants. For level 1 systems in health care occupancies, the risk of loss of life is high.

Another factor to consider is the physical arrangement of the equipment. In this case, the EPSS equipment was directly across from the normal service equipment. The age of the equipment is another useful factor due to the understanding that older equipment can have a higher chance of catastrophic failure. There are many facilities across the country that have a similar physical arrangement, and corrective action should be reviewed in all instances.

To determine an appropriate scope for the project, the first step was to perform a detailed study that identified three primary areas requiring correction:

• The physical location of the EPSS equipment.
• The configuration and condition of the EPSS distribution, which did not meet the vertical segregation requirement of NEC Art 700.10.
• The comingling of emergency loads at the branch circuit level.

It was discovered that there was a lack of subdivision of the proper emergency branches as required by NFPA 70: National Electrical Code Article 517. The code requires separation of life safety, critical and equipment with very specific loads permitted on each branch and like many facilities of this vintage, proper separation did not exist. The study identified the need to correct the branch circuit separation at the panelboard level to rightly assign branches at the transfer switch level.

The result of the study spawned a project with a clearly defined scope to upgrade the EPSS and bring the aged system up to current codes and standards. The next challenge was phasing and constructability. An electrical infrastructure upgrade project in a fully operational hospital impacts the clinical teams and patient care areas alike. The electrical distribution changes create outages that inevitably impact the ability for the facility to provide care to patients without the proper planning. This requires a concerted team effort between the owner, design engineer and construction team to plan all outages with the least amount of impact to patient care.

An impact assessment should be performed by the engineer, in cooperation with the facility, to identify and document the plan during the design phase. Some solutions may result in increased costs or complexity and some solutions may be a total departure from initial assumptions.

For this project, a local electrical contractor with decades of on-site experience was engaged to be a part of the design team and they participated in meetings with the facility and clinical representatives to determine what impacts each ATS replacement would have. The input provided by the electrical contractor was incredibly valuable and most instances included a story that went something like “the last time we had to shut that down we learned this…”

Being able to learn from the past to improve the future plan is key. As a result, the drawings did not rely on a single, overall one-line diagram that simply showed demo and new scope as an initial and final arrangement. Instead, each ATS was given its own diagram with every panel served by the ATS identified and specific notes for the outage mitigation strategy.

Some strategies allowed for outages at certain time frames or seasons (when equipment was involved). Some strategies required temporary power for loads, with the source of the temporary power identified. The notes went into detail of what to do with the old ATS location and options included to remove the cabinet and refeed the load or reuse the cabinet as a junction box or to remove the cabinet and intercept the feeder elsewhere in the path. Each option carries a different outage timeframe and thus a unique strategy.

Some of the challenges uncovered with this project that required close coordination were:

• The entire surgical department was on a single emergency feeder without a second emergency or normal source available in the rooms. Changing the ATS feeding this department would result in a complete outage of the department.
• When the distribution upgrades affect the elevators, the ability to transport patients is affected. This requires coordination during design for where patients will need to be moved to during the outage, if an emergent case requiring transport to a caesarian-section room or operating room is required during the outage.
• Outages affecting imaging equipment required a coordinated shutdown effort because the uninterruptable power supply duration would be exceeded.
• The Information technology and information systems departments are also vital to the operability of a health care facility, and while those systems are usually on a UPS, the available runtime needed to be evaluated along with the expected outage duration and risk associated with the outage lasting longer than expected.

The new design took all of these aspects into consideration by creating two new EPSS electrical rooms to house new, code-compliant distribution and new ATS equipment. To mitigate extended outages to the entire emergency system, separate feeders were routed to the existing generator paralleling gear. The latest editions of NFPA 110, NFPA 70 and NFPA 99: Health Care Facilities Code were strictly followed to provide the most reliable system possible.

The design also provided a consistent nomenclature across the entire facility’s EPSS. The new naming convention included the existing name as the first characters then added a unique number (if missing), along with an abbreviation for the branch. For example: ATS-6 would become ATS-6CR, thereby providing a concise reference as to which branch the system fed. Changing names of panels or equipment in existing facilities must be done with great care due to the impact it can have on existing labeling in junction boxes, equipment or panels.

The branch panel comingling was evaluated largely impart to a previous effort by the facility to update all of the branch panel schedules and physical testing of each circuit. With this in hand, the design team recommended individual circuit relocations and provided a design for additional panelboards where necessary. The end result is a design that adheres to the currently adopted editions of all applicable codes. New equipment installations must comply with adopted codes for working clearances, overcurrent protection, coordination and environment.

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